Interstitial 125-iodine radiosurgery of low-grade gliomas of the insula of Reil

Beyond surgical resection: evaluating stereotactic brachytherapy iodine-125 for low-grade gliomas: a systematic review and meta-analysis

Stereotactic Brachytherapy Iodine-125 (SBT I-125) has been investigated by some studies for the treatment of lowgrade gliomas. We performed a meta-analysis to assess the efficacy and safety of SBT I-125 Brachytherapy for treatment of patients with Low-Grade Gliomas. PubMed, Cochrane, Web of Science, and EMBASE databases were searched for randomized and observational studies. This systematic review and meta-analysis was conducted according to the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines. We used relative risk (RR) with 95% confidence intervals and random effects model to compare the effects of I-125 SBT treatment on the interest outcomes. We evaluated heterogeneity using I2 statistics; we considered heterogeneity to be significant if the p-value was less than 0.05 and I2 was higher than 35%. We performed statistical analysis using the software R (version 4.2.3). A total of 20 studies with a cohort of 988 patients with low grade gliomas who received SBT I-125 as a treatment option. The pooled analysis evidenced: (1) Complication rate of 10% (95% CI: 7-12%; I² = 60%); (2) 5-year PFS of 66% (99% CI: 45-86%; I²= 98%); (3) 10-year PFS was 66% (99% CI: 45-86%; I²= 98%); (4) Malignant transformation rate of 26% (95% CI: 8-45%; I²=0); (5) Mortality of 33% (95% CI: 15-51%; I² = 0%). Our systematic review and meta-analysis of SBT I-125 for low-grade gliomas have revealed significant concerns regarding its safety and efficacy. Despite a proportion of patients remaining progression-free, elevated rates of complications and mortality cast doubt on the intervention's reliability. Future research should prioritize long-term follow-up studies, standardized protocols, and comparative effectiveness research.

Prognostic Factors and Resectability Predictors in Insular Gliomas: A Systematic Review

BACKGROUND

 Insular gliomas (INGs) remain a surgically intimidating glioma subgroup encased by eloquent cortical parcels and white matter language tracts, and traversed by multiple middle cerebral artery branches. The predictive power of prognostic factors affecting overall survival (OS), progression-free survival (PFS), and resectability of INGs remain disputed. This comprehensive systematic review analyses prognostic factors and resectability predictors of INGs substantiating pragmatic management options.

MATERIALS AND METHODS

 A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) and the Cochrane Handbook of Systematic Reviews of Interventions guidelines. The PubMed, MEDLINE, and Embase databases were searched in April 2022. All clinical studies with ≥10 patients harboring INGs with any intervention and reporting predictors of OS, PFS, and tumor resectability in INGs were included. Molecular ING prognosticators were also included. Studies combining insular and other gliomas analysis, case studies, experimental and animal studies, conference abstracts, letters to the editor, and articles in other languages were excluded.

RESULTS

 Of the 2,384 articles returned, 27 fulfilled the inclusion criteria totaling 1,985 patients. The review yielded 18 OS and 17 PFS prognosticators. These were classified as preoperative (radiologic; clinical), intraoperative, and postoperative (molecular; histopathologic; clinical) prognosticators. In addition, 21 resectability predictors were categorized as preoperative (radiologic; clinical), intraoperative (surgical approach and assistive technology), and postoperative (histopathologic; clinical). The quality assessment revealed 24/27 studies had low risk of bias. One study with moderate and two studies with high risk of bias were included.

CONCLUSION

 Negative prognosticators reported in ≥2 studies included putaminal or paralimbic involvement and higher tumor grade, while seizures at presentation, isocitrate dehydrogenase (IDH) mutation, increased extent of resection, and higher Karnofsky Performance Status preoperatively and at 3 months postoperation were positive prognosticators. Resectability predictors reported in ≥2 studies included the positive predictors of zone I/zone IV tumor location and intraoperative imaging use and the negative predictor of encased lenticulostriate arteries. Paralimbic INGs are not a single entity with homogeneous prognosis. Integration of identified prognosticators in a prospective trial to devise a grading system for INGs can improve clinical decision-making.

Preservation of the Lenticulostriate Arteries During Insular Glioma Resection

Insular gliomas represent 25% and 10% of low- and high-grade gliomas, respectively. Their resection proves challenging due to the intimate involvement of eloquent parenchyma and the lenticulostriate arteries (LSAs), limiting facility of achieving maximal safe resection. The majority of postoperative deficits following insular glioma resection is attributed to compromise of the LSAs. It is contemporaneously critical and challenging to preserve these vessels, given they are numerous and small, with an intraparenchymal course hidden from direct visualization during the operative intervention. A lesser degree of medially directed displacement of the LSAs predicts tumoral encasement of these vessels, which portends a decreased likelihood for achieving a gross total resection and increased probability of postoperative morbidity. Preservation of these vessels thus requires knowledge of their location during the entirety of the insular glioma resection and is facilitated by pre- and intra-operative imaging. Intraoperative real-time tracking, however, may prove rather challenging, especially with transcortical access. Conventional catheter digital subtraction angiography, computed tomographic angiography, magnetic resonance imaging and angiography, and three-dimensional ultrasound powered Doppler have proven effective modalities in assessing lenticulostriate position, and their use facilitates a greater extent of resection while minimizing the attendant morbidity consequent to LSA injury.

The role of radiotherapy in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTIONS

(1) What is the optimal role of external beam radiotherapy in the management of adult patients with newly diagnosed low-grade glioma (LGG) in terms of improving outcome (i.e., survival, complications, seizure control or other reported outcomes of interest)? (2) Which radiation strategies (dose, timing, fractionation, stereotactic radiation, brachytherapy, chemotherapy) improve outcomes compared to standard external beam radiation therapy in the initial management of low grade gliomas in adults? (3) Do specific factors (e.g., age, volume, extent of resection, genetic subtype) identify subgroups with better outcomes following radiation therapy than the general population of adults with newly diagnosed low-grade gliomas?

TARGET POPULATION

These recommendations apply to adults with newly diagnosed diffuse LGG.

RECOMMENDATIONS

OUTCOMES IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level I Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong progression free survival, irrespective of extent of resection. Level II Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults as an equivalent alternative to observation in preserving cognitive function, irrespective of extent of resection. Level III Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults to improve seizure control in patients with epilepsy and subtotal resection. Level III Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong overall survival in patients with subtotal resection. Level III Consideration of the risk of radiation induced morbidity, including cognitive decline, imaging abnormalities, metabolic dysfunction and malignant transformation, is recommended when the delivery of radiotherapy is selected in the management of newly diagnosed low-grade glioma in adults. STRATEGIES OF RADIOTHERAPY IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA: Level I Lower dose radiotherapy is recommended as an equivalent alternative to higher dose immediate postoperative radiotherapy (45-50.4 vs. 59.4-64.8 Gy) in the management of newly diagnosed low-grade glioma in adults with reduced toxicity. Level III Delaying radiotherapy until recurrence or progression is recommended as an equivalent alternative to immediate postoperative radiotherapy in the management of newly diagnosed low-grade glioma in adults but may result in shorter time to progression. Level III The addition of chemotherapy to radiotherapy is not recommended over whole brain radiotherapy alone in the management of low-grade glioma, as it provides no additional survival benefit. Level III Limited-field radiotherapy is recommended over whole brain radiotherapy in the management of low-grade glioma. Level III Either stereotactic radiosurgery or brachytherapy are recommended as acceptable alternatives to external radiotherapy in selected patients. PROGNOSTIC FACTORS IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level II It is recommended that age greater than 40 years, astrocytic pathology, diameter greater than 6 cm, tumor crossing the midline and preoperative neurological deficit be considered as negative prognostic indicators when predicting overall survival in adult low grade glioma patients treated with radiotherapy. Level II It is recommended that smaller tumor size, extent of surgical resection and higher mini-mental status exam be considered as positive prognostic indicators when predicting overall survival and progression free survival in patients in adult low grade glioma patients treated with radiotherapy. Level III It is recommended that seizures at presentation, presence of oligodendroglial histological component and 1p19q deletion (along with additional relevant factors-see Table 1) be considered as positive prognostic indicators when predicting response to radiotherapy in adults with low grade gliomas. Level III It is recommended that increasing age, decreasing performance status, decreasing cognition, presence of astrocytic histological component (along with additional relevant factors (see Tables 1, 2) be considered as negative prognostic indicators when predicting response to radiotherapy.

[Review of surgical treatment of insular gliomas: challenges and opportunities]

Intracerebral tumors of the insular lobe are quite frequent, however treatment of patients with this pathology still remains a challenging and controversial issue of neurosurgery. First of all, this is associated with the localization of tumors in the area of eloquent anatomical structures: M1--M2 segment of the middle cerebral artery, lenticulostriate arteries, basal ganglia, and internal capsule, which causes a high rate of postoperative complications in these patients. Most insular tumors are amenable for resection with a reasonable rate of postoperative complications, although most of the surgery-related complications resulting in substantial deficits are due to lesions of eloquent anatomical structures located in this compact anatomical space. Therefore, the aim of this work was to analyze the literature regarding the issues of clinical presentation, diagnosis, and aspects of surgical treatment of insular tumors.

Surgery of insular nonenhancing gliomas: volumetric analysis of tumoral resection, clinical outcome, and survival in a consecutive series of 66 cases

BACKGROUND

Despite intraoperative technical improvements, the insula remains a challenging area for surgery because of its critical relationships with vascular and neurophysiological functional structures.

OBJECTIVE

To retrospectively investigate the morbidity profile in insular nonenhancing gliomas, with special emphasis on volumetric analysis of tumoral resection.

METHODS

From 2000 to 2010, 66 patients underwent surgery. All surgical procedures were conducted under cortical-subcortical stimulation and neurophysiological monitoring. Volumetric scan analysis was applied on T2-weighted magnetic resonance images (MRIs) to establish preoperative and postoperative tumoral volume.

RESULTS

The median preoperative tumor volume was 108 cm. The median extent of resection was 80%. The median follow-up was 4.3 years. An immediate postoperative worsening was detected in 33.4% of cases; a definitive worsening resulted in 6% of cases. Patients with extent of resection of > 90% had an estimated 5-year overall survival rate of 92%, whereas those with extent of resection between 70% and 90% had a 5-year overall survival rate of 82% (P < .001). The difference between preoperative tumoral volumes on T2-weighted MRI and on postcontrast T1-weighted MRI ([T2 - T1] MRI volume) was computed to evaluate the role of the diffusive tumoral growing pattern on overall survival. Patients with preoperative volumetric difference < 30 cm demonstrated a 5-year overall survival rate of 92%, whereas those with a difference of > 30 cm had a 5-year overall survival rate of 57% (P = .02).

CONCLUSION

With intraoperative cortico-subcortical mapping and neurophysiological monitoring, a major resection is possible with an acceptable risk and a significant result in the follow-up.

The place of interstitial brachytherapy and radiosurgery for low-grade gliomas

Even though stereotactic brachytherapy has been used for treatment of complex located low-grade glioma for many years, its place within modern treatment concepts is still debated and only a few centers have gained experience with this complex treatment modality. The current article reviews selection criteria, treatment protocols, radiobiology, treatment effects, risk models and side effects of stereotactic brachytherapy. Potentially alternative techniques such as radiosurgery were also reviewed under consideration of radiobiological similarities and differences.

Subcortical mapping and monitoring during insular tumor surgery

Object

The treatment of insular tumors is controversial. Surgical treatment is associated with a higher morbidity rate than other therapies. The present work presents a new method in which the descending motor pathways are monitored during surgery for insular tumors.

Methods

Intraoperative monitoring was performed in a combination of 2 techniques. The motor cortex was stimulated with a transcranial electrical stimulus. In addition, direct subcortical stimulation was performed with an electrical anodal monopolar stimulus. Compound motor action potentials (CMAPs) were recorded from target muscles.

Results

Fifteen patients were included in this preliminary study. Following transcranial stimulation, CMAPs were recorded in all cases. Subcortical stimulation was successful in 12 cases. Significant CMAP alterations were recorded in 5 patients. There were no false-negative results in the series.

Conclusions

The technique presented here is a safe method. It allows a quantitative monitoring of motor function and functional mapping of the pyramidal tract during insular surgery.

Insular gliomas: the case for surgical management

Object

Treatment for insular (paralimbic) gliomas is controversial. In this report the authors summarize their experience with microsurgical resection of insular tumors.

Methods

The authors analyzed complications, functional outcomes, and survival in a series of 101 operations performed in 94 patients between 1995 and 2005.

Results

A > 90% resection was achieved in 42%, and 70–90% tumor removal was accomplished in 51% of cases. Functional outcomes varied considerably between patient subgroups. For example, in neurologically intact patients ≤ 40 years of age with WHO Grade I–III tumors, good outcomes (Karnofsky Performance Scale Score 80–100) were seen in 91% of cases. Predictors of an unfavorable functional outcome included histological features of glioblastoma, advanced age, and a low preoperative Karnofsky Performance Scale score. One year after surgery, 76% of patients who had presented with epilepsy were seizure free or experienced only isolated, nondebilitating seizures. Surprisingly good survival rates were seen after surgery for anaplastic gliomas. The median survival for patients with anaplastic astrocytomas (WHO Grade III) was 5 years, and the 5-year survival rate for those with anaplastic oligodendroglial tumors was 80%. Independent predictors of survival included younger age, favorable histological features (WHO Grade I and oligodendroglial tumors), Yaşargil Type 5A/B tumors with frontal extensions, and more extensive resections.

Conclusions

Insular tumor surgery carries substantial complication rates. However, surprisingly similar figures have been reported in large unselected craniotomy series and also after alternative treatment regimens. In view of the oncological benefits of resective surgery, our data would therefore argue for microsurgery as the primary treatment for most patients with a presumed WHO Grade I–III tumor. Patients with glioblastomas and/or age > 60 years require a more cautious approach.

Resection of insular gliomas: the importance of lenticulostriate artery position

OBJECT

The object of this study was to identify characteristic preoperative angiographic and MR imaging features of safely resectable insular gliomas and describe the surgical techniques and postoperative clinical outcomes.

METHODS

Thirty-eight patients with insular gliomas underwent transsylvian resection between 1995 and 2007. Patient demographics, presenting symptoms, pathological findings, and neurological outcomes were retrospectively reviewed. Preoperative MR imaging-defined tumor volumes were superimposed onto the preoperative stereotactic cerebral angiograms to determine whether the insular tumor was confined lateral to (Group I) or extended medially around (Group II) the lenticulostriate arteries (LSAs).

RESULTS

Twenty-five patients (66%) had tumors situated lateral to the LSAs and 13 (34%) had tumors encasing the LSAs. Insular gliomas situated lateral to the LSAs led to significant medial displacement of these vessels (161 +/- 39%). In 20 (80%) of these 25 cases the boundaries between tumor and brain parenchyma were well demarcated on preoperative T2-weighted MR images. In contrast, there was less displacement of the LSAs (130 +/- 14%) in patients with insular gliomas extending around the LSAs on angiography. In 11 (85%) of these 13 cases, the tumor boundaries were diffuse on T2-weighted MR images. Postoperative hemiparesis or worsening of a preexisting hemiparesis, secondary to LSA compromise, occurred in 5 patients, all of whom had tumor volumes that extended medial to the LSAs. Gross-total or near-total resection was achieved more frequently in cases in which the insular glioma remained lateral to the LSAs (84 vs 54%).

CONCLUSIONS

Insular gliomas with an MR imaging-defined tumor volume located lateral to the LSAs on stereotactic angiography displace the LSAs medially by expanding the insula, have well-demarcated tumor boundaries on MR images, and can be completely resected with minimal neurological morbidity. In contrast, insular tumors that appear to surround the LSAs do not displace these vessels medially, are poorly demarcated from normal brain parenchyma on MR images, and are associated with higher rates of neurological morbidity if aggressive resection is pursued. Preoperative identification of these anatomical growth patterns can be of value in planning resection.

Surgical resection plus stereotactic 125I brachytherapy in adult patients with eloquently located supratentorial WHO grade II glioma - feasibility and outcome of a combined local treatment concept

OBJECTIVE

The current pilot study analyzed feasibility, risk and effectiveness of 1) microsurgery plus stereotactic iodine-125 ((125)I) brachytherapy (SBT) for large (diameter > 4 cm), circumscribed, and complex located WHO grade II glioma and 2) SBT alone for small (diameter < 4 cm), and complex located recurrences.

METHODS

Lowactivity temporary (125)I seeds were used. The applied reference dose was 54 Gy and the dose rate was low (median, 10 cGy/h). Time to progression and time to additional external beam radiation (EBR) and/or chemotherapy were estimated with the Kaplan-Meier method. Any adverse sequel potentially attributable to treatment was classified as morbidity. Treatment effects of SBT were estimated according to the modified MacDonald criteria.

RESULTS

Thirtyone patients (de novo group: n = 18, recurrence group: n = 13) were included. The median tumor volume before surgery was 66 ml. A planned partial tumor resection achieved eligibility for SBT in all patients. Transient morbidity of microsurgery and SBT was 27.8 % and 6.4 %, respectively. There was no permanent morbidity. Radiogenic complications did not occur. Complete response, partial response, and stable disease were seen in 8, 9, and 14 patients, respectively. Ten patients exhibited tumor progression (overall 5-year progression- free survival > 60 %). The 5-year probability to receive chemotherapy and/or EBR was 18 %.

CONCLUSION

A planned partial tumor resection of large and complex located WHO grade II glioma is safe. SBT of small and complex located residual of recurrent tumors is safe and minimally invasive. Combined treatment may provide the possibility to withhold EBR and/or chemotherapy for a considerable number of patients and deserves further prospective evaluation.

Interstitial stereotactic radiosurgery of pilocytic astrocytomas in paediatric patients

OBJECTIVE

To evaluate the clinical presentation, tumour response, clinical improvement and complications in 12 children and young people with a pilocytic astrocytoma, WHO I grade 1, who were treated with interstitial radiosurgery using Iodine-125 seed implants.

PATIENTS AND METHODS

Retrospective analysis of 12 patients aged under 18 years (mean 8.4 years, ranging from 8 months to 17 years of age) with a pilocytic astrocytoma treated between 1993 and 2006. Iodine-125 seeds were used as temporary implants with low-dose rate (<or=10 cGy/h) and a calculated reference dose of 60 and 100 Gy to the outer ring of the tumour.

RESULTS

There was no perioperative mortality. Two patients worsened transiently, but thereafter each patient improved clinically. Eleven out of 12 tumours shrank after the treatment. The mean volume of the tumours before implantation was 17.9 cm(3). and was reduced to 60% of this volume at 6 months, to 26.5% at 12 months, to 8% at 24 months, and was less than 1% at 30-36 months One patient underwent a reimplantation to treat a recurrence 3 years after the initial treatment. Ten patients were alive 2 years after the first intervention. In the longest surving patient, there was no evidence of progression after 13.4 years of follow up.

Motor tract monitoring during insular glioma surgery

Object

Surgery for insular gliomas incurs a considerable risk of motor morbidity. In this study the authors explore the validity and utility of continuous motor tract monitoring to detect and reverse impending motor impairment during insular glioma resection.

Methods

Motor evoked potentials (MEPs) were successfully monitored during 73 operations to remove insular gliomas. Seventy-two cases were assessable, and one patient died during the early postoperative course. In this prospective observational approach, MEP monitoring results were correlated with intraoperative events and perioperative clinical data.

Intraoperative recordings of MEPs remained stable in 40 cases (56%), indicating unimpaired motor outcome and allowing safe completion of the hazardous steps of the procedure. Deterioration of MEPs occurred in 32 cases (44%). This deterioration was reversible after intervention in 21 cases (29%), and there was no new motor deficit except for transient paresis in nine of these cases (13%). Surgical measures could not prevent irreversible MEP deterioration in 11 cases (15%). Transient mild or moderate paresis occurred if complete MEP loss was avoided. Irreversible MEP loss in seven cases (10%) occurred after completion of resection in four of these seven cases, and was consistently an indicator of both a stroke within the deep motor pathways and permanent paresis, which remained severely disabling in three patients (4%). In contrast, permanently severe paresis occurred in two (18%) of 11 cases without useful MEP monitoring.

Conclusions

Continuous MEP monitoring is a valid indicator of motor pathway function during insular glioma surgery. This method indicates that remote ischemia, in this study the leading cause of impending motor deterioration, helps to avert definitive stroke of the motor pathways and permanent new paresis in the majority of cases. The rate of permanently severe new deficit appears to be greater in unmonitored cases.

Brachytherapy for brain tumors

Over the past several decades neurooncologists have attempted to find an adjuvant treatment that prolongs survival for patients with malignant brain tumors. Brachytherapy, radiotherapy delivered by placing radioactive sources directly into the tumor, was initially thought to be the solution to this problem. Initial single institution studies showed very promising results; however, this technique has failed to show a significant survival advantage in two randomized studies. Despite this, brachytherapy continues to be used in a number of centers throughout the world for the treatment of various types of brain tumors including low-grade gliomas, anaplastic astrocytomas, glioblastomas, meningiomas and metastases. This article reviews brachytherapy's rationale, radiobiology, complications, indications, and results from numerous studies that have focused on its application for brain tumors with emphasis on its application for glial tumors.

The insular lobe and brain plasticity: Lessons from tumor surgery

OBJECTIVES

Despite recent literature supporting the likely role of the insula in many functions, the actual participation of this multimodal lobe in the brain functioning remains unclear, i.e. has the insula an essential or compensable role?

PATIENTS AND METHODS

We surgically resected an insular low-grade glioma, using intraoperative electrical stimulation, in 42 patients who experienced seizures, but who presented no or only a slight neurological deficit. Surgery was performed under local anesthesia in patients with a lesion in the dominant hemisphere. The resection was systematically stopped according to cortico-subcortical functional boundaries.

RESULTS

Intraoperative electrical mapping induced language disturbances, pain and vertigo, but no other side effects were observed. Post-operatively, the patients experienced a transient hemiparesis in 21 cases, language disorders in 10 cases, an athymhormic syndrome in 7 cases, a Foix-Chavany-Marie syndrome in 3 cases, and micturition disturbances in one case. Despite this immediate post-surgical worsening, all the patients recovered their preoperative neurological status within 3 months, except in three cases due to a deep stroke.

CONCLUSION

These results show that the insula, a complex associative multimodal structure poorly studied until now, can be functionally compensated. Such a plastic potential may have important fundamental and clinical implications, in particular in the field of oncological neurosurgery.

Long term course of WHO grade II astrocytomas of the Insula of Reil after I-125 interstitial irradiation

OBJECTIVE

To present long-term results after interstitial iodine-125 irradiation of adult patients with de-novo World Health Organization (WHO) Grade II astrocytomas and oligoastrocytomas of the insula of Reil with special respect to the treatment-related risk.

METHODS

55 consecutively treated patients (from 1979 to 1992) with circumscribed tumors with a diameter < 5 cm (astrocytomas: 46 patients, oligoastrocytomas: 9 patients) were included. The reference dose-calculated to the outer boundary of the tumor-was in the range of 60-100 Gy and the dose rate was low (< 10 cGy/h). Progression-free survival, risk of malignant transformation, survival, and the incidence of radiogenic complications were estimated by the Kaplan-Meier method. Prognostic factors were obtained from the Cox-model.

RESULTS

Median follow up for the survivors was > 10 years. 5-year (10-year) progression-free survival was 40.7 % (20.2 %), and 5-year (10-year) survival 54.6 % (28.4 %). Malignant transformation occurred in 42.4 % after 5 years. Neither of the Kaplan-Meier curves showed a leveling off over time. Transient (progressive) radiogenic complications were observed in 13 [4] patients (one-year overall complication rate: 18%), and were significantly associated with a tumor diameter >3.5 cm (p<0.001). No long term side-effects were detected and delayed external beam irradiation (in case of tumor progression) did not enhance the risk. Tumor enhancement on CT was the only unfavorable predictor for survival.

CONCLUSION

A limited overall prognosis for adult patients with insular WHO grade II astrocytomas and oligoastrocytomas was detected. Interstitial I-125 irradiation offers a minimal-invasive and low-risk treatment option for circumscribed tumors with a diameter < 3.5 cm. Larger tumors require further evaluation for optimal treatment.

Interstitial stereotactic radiosurgery

Stereotactic radiosurgery by means of interstitial application of either radionuclides or radiation devices has been used extensively in primary and secondary brain tumors. A few centers have gained sufficient expertise and clinical data to scientifically evaluate this treatment modality. Interstitial stereotactic radiosurgery is limited to circumscribed lesions with a diameter of 3.5 cm or less. The radiobiology of interstitial radiosurgery is quite well elaborated as to doses, dose rates and effects on vascular physiology. Efficacy in low grade gliomas is well documented by several European centers using 125-J sources. Different modes of implantation have been used and evaluated including single fraction treatment using a miniature linear accelerator (Photoelectron). In malignant gliomas interstitial radiosurgery has been investigated in a prospective, randomised, controlled trial and not shown to be effective. Steretactic interstitial radiosurgery is a powerful treatment option in circumscribed CNS tumors like some low grade gliomas and metastasis but does play no major role in the treatment of malignant glioma.

Surgical resection of intrinsic insular tumors: complication avoidance

OBJECT

Surgical resection of tumors located in the insular region is challenging for neurosurgeons, and few have published their surgical results. The authors report their experience with intrinsic tumors of the insula, with an emphasis on an objective determination of the extent of resection and neurological complications and on an analysis of the anatomical characteristics that can lead to suboptimal outcomes.

METHODS

Twenty-two patients who underwent surgical resection of intrinsic insular tumors were retrospectively identified. Eight tumors (36%) were purely insular, eight (36%) extended into the temporal pole, and six (27%) extended into the frontal operculum. A transsylvian surgical approach, combined with a frontal opercular resection or temporal lobectomy when necessary, was used in all cases. Five of 13 patients with tumors located in the dominant hemisphere underwent craniotomies while awake. The extent of tumor resection was determined using volumetric analyses. In 10 patients, more than 90% of the tumor was resected; in six patients, 75 to 90% was resected; and in six patients, less than 75% was resected. No patient died within 30 days after surgery. During the immediate postoperative period, the neurological conditions of 14 patients (64%) either improved or were unchanged, and in eight patients (36%) they worsened. Deficits included either motor or speech dysfunction. At the 3-month follow-up examination, only two patients (9%) displayed permanent deficits. Speech and motor dysfunction appeared to result most often from excessive opercular retraction and manipulation of the middle cerebral artery (MCA), interruption of the lateral lenticulostriate arteries (LLAs), interruption of the long perforating vessels of the second segment of the MCA (M2), or violation of the corona radiata at the superior aspect of the tumor. Specific methods used to avoid complications included widely splitting the sylvian fissure and identifying the bases of the periinsular sulci to define the superior and inferior resection planes, identifying early the most lateral LLA to define the medial resection plane, dissecting the MCA before tumor resection, removing the tumor subpially with preservation of all large perforating arteries arising from posterior M2 branches, and performing craniotomy with brain stimulation while the patient was awake.

CONCLUSIONS

A good understanding of the surgical anatomy and an awareness of potential pitfalls can help reduce neurological complications and maximize surgical resection of insular tumors.

Surgical treatment of insular gliomas

Surgical treatment of glial tumours arising in the insula is specially challenging due to the proximity of the internal capsule. Although small insular gliomas have been removed safely by a transylvian approach, in large dominant insular tumours only biopsy has been recommended to avoid postoperative deficits. Unfortunately that is a suboptimal form of treatment as low grade supratentorial gliomas should be removed radically to prevent tumour progression, malignization and to increase the recurrence-free-interval. Addition of radiotherapy to partial removal is associated with a much higher incidence of recurrences and early malignizations compared to radical removal and no radiotherapy. Between 1st October 1989 and 1st September 1996 we treated twenty-three patients harbouring insular gliomas. To increase the radicality of the resection the surgical procedure was performed under local anaesthesia whenever possible, as general anaesthesia usually leads to more conservative resections. In 20/23 (86.9%) patients complete resection was accomplished, and subtotal in three (13.1%). The removed tumours were: two oligodendrogliomas, five grade I astrocytomas, nine grade II, four grade III and three grade IV. Postoperative neurological deficits occurred in five patients. Four suffered a hemiparesis (that recovered in an average of 6 months) and one a motor dysphasia which took a week to recover. Two of the seventeen patients operated on for low grade insular gliomas underwent malignant change. We conclude that complete surgical removal of insular gliomas should be considered and at least attempted in all cases.

Intrinsic tumors of the insula: a prospective surgical study of 30 patients

Intrinsic insular tumors are frequently excluded from surgical treatment. The authors propose a more extensive approach to these lesions based on the results of this prospective series. From September 1993 to January 1995, 30 patients (18 males and 12 females; mean age 42 years) harboring benign (15 patients) or malignant (15 patients) tumors involving the insula underwent surgical treatment. The dominant and nondominant hemispheres were both affected in 15 cases. Two groups were defined on the basis of preoperative magnetic resonance (MR) imaging: 14 lesions were restricted to the insula and the corresponding opercula; the other 16 lesions also involved other mesocortical and/or allocortical areas. Most patients displayed only mild preoperative symptoms. The median score according to the Karnofsky performance scale was 90. Microsurgical removal was achieved via a transsylvian approach in nine cases and via a frontal and/or temporal approach in 21 cases. According to early postoperative MR imaging, complete tumor removal (100%) was seen in five patients, nearly complete (> 80%) in 21, and incomplete resection (50%-80%) in four patients. There was no operative mortality; 19 patients (63%) experienced immediate postoperative morbidity, including reduced performance. After a mean follow-up review of 8.5 months two of 21 patients suffered permanent deficits, accounting for an overall operative morbidity of 10%. At the mean time of review, three patients with Grade IV tumors had died of tumor recurrence. The authors conclude that low-grade intrinsic insular tumors, as well as Grade III tumors, can be removed with favorable results in the majority of patients. Surgery to excise glioblastomas should only be considered for patients with good preoperative performance and young age.